Methods of making light weight heat insulating blocks



Bischoff, Hagen, Westphalia, Germany, assignors to Example 1.Sintereddolomite, stabilized with silicig Dolomitwel'ke Wulfrath, Rhineland, flLand hydraulically sefimg, and sufiiciently ground to y, a f 'p f ofGermany provide a 4% residue on the 4900-mesh screen, was pre- NoDrawing. Frled July 21, 1961, Ser. No. 125,664

claims priority application Germany July 25 1960 pared as a plastic andas a thln llqllld pulp by adding a 5 ms. (Cl. H sufiicient amount ofwater. Then, as it is done durmg 10 the production of air entrainingconcrete, aluminum To decrease the LQSLOLhQLtiH industrial furnaces,heat der was added as amb'd'fiing agent -("03% by weight insulating andsufiiciently fireproo or light in relation to the ground sintereddolomite). weight blocks are inserted, usually as a back-wall con- Thispowder was quickly and intensively intermixed, struction. Shouldsintered dolomite brick be used as a whereupon the preparation was castinto molds in which working lining in order to provide a basic coatingcapable the pulp was expanded by the generation of gas. After ofwithstanding a high temperature, such are suitable for a hydraulichardening of three days, the resulting molded instance in steel-, lime-,and cement-turn ces, then, as a body was taken from the shell, thenbroken into granules heat insulating layer, lying Behind such workinglining, having a particle size no larger than 30 mm., and this brobasiclight weight blocks are best suited to avoid undeken material wastempered for fifteen hours in a tunnel sirable chemical reactions withthe sintered dolomite on furnace which reached approximately 1500 C. inits hot the contact surface. Of course, most successful are light zone.From the resulting well-hardened granulated maweight blocks of amaterial of the same kind, that is terial, the grain 7-15 mm. was siftedoff. From the latdolomite itself. ter molded bodies were then producedby adding water It has been suggested, although not yet in technologicaland 20% by weight of sintered dolomite, ground as fineuse, that suchdolomite li ht-weight blocks may be proly as Portland cement, forexample, with a 4% residue duced from ground, stabilized andhydraulically setting on the 4900-mesh screen, stabilized andhydraulically sintered dolomite, by simply pre-mixing it with water tosetting. By shaking such mixture the grains were brought form a plastic,to a thinly liquid pulp, adding a pore-prointo close relation with eachother. After a hydraulic dueing material, such as aluminum or ma esiumpowder, hardening of seven days, a resistance to cold pressure orremmmiiHmereof 40 kg./cm. was observed with a volumetric weight by gasor air pores are produced, and then permitting the (bulk density) of 0.9kg./ltr. The linear shrinkage was mass hydraulically to harden in molds.Such dolomite 1.8% with a temperature of 1500 C. light-weight blocks aregood heat insulators and are re- Example 2.By cautious stamping moldedbodies were sistant to high temperatures, with a melting point aboveproduced in the same way from the unsifted granula- 1900 0, However, aserious disadvantage is their tendtion which had a particle size nolarger than 30 mm. ency to shrink and to form cracks, especially attemperaafter a temperature treatment in the tunnel furnace, again turesabove 1100 C. With a 20% addition of the before mentioned hydraulic Thepresent invention is concerned with an improvebinder. These moldedbodies had a more compact struc ment of such dolomite light-weightblocks, especially reture and the volumetric wei ht was 1.4 k ./ltr.After garding the shrinkage and fissuring as mentioned. Aca hydraulicharcEii HsfWeh'Wt'EE da flty was cording to the invention the porousmolded bodies of around 85 k ./cm. The shrinkage amounted mm? dolomite,as described above, after a more or less com- It'slfifild'fiemed that indefining the preferred fineplete hydraulic setting are submitted to aburning or temness of the sintered dolomite employed in the foregoingpering process desirably above 1200" C. or, even better, examples as4900mesh, this is according to the convenabove 1400 C. In thisconnection it is of advantage to tional European scale. The equivalentTyler Standard choose not too large a size for the molded bodies ofdoscreen size generally used in the United States would be lomite, orto-break them in advance, in order to facilitate approximately ljlmesh.corresponding with an 0.0035 uniform shrinkage throughout during thetempering procin. opening. ess. The pieces desirably should be smallerthan 200 Other modes of applying the principle of the invention mm. andeven better smaller than 100 mm. The tempermay be employed, change beingmade as regards the deing process may be satisfactorily carried out, forinstance, tails described, provided the means, the steps of the methbypassing such pieces through a tunnel furnace for sevod or thecharacteristics of the product stated in any of eral hours, as a rulebetween five and forty hours, dethe following claims, or the equivalentof such, be empending on size and temperature. During this processployed. each single piece will shrink, but an agglomeration of Wetherefore particularly point out and distinctly claim them will beavoided. as my invention:

From such tempered material, new molded bodies of l. A method ofproducing 21W any preferred size can be produced, preferably again bying body having a reduced ten ency to shrink and form using finelyground, stabilized and hydraulically setting cracks comprising the stepsof admixing stabilized sinsintered dolomite, in the regular way, just asin the case tered hydraulically settable dolomite, at least 96 percentof regular concrete. After their hydraulic hardening these by weight ofwhich passes a Tyler Standard screen size new molded bodies can bedirectly installed as heat inof 170, with sufiicient water to formcastable hydraulical-' sulating dolomite light-weight blocks, forinstance, behind ly settable pulp and with a metallic pore-producingagent 1 the basic working lining. selected from the group consisting ofaluminum and mag- Dolomite light-weight blocks, produced in this way,nesium present in an amount sufiicient to elfect expansion i have only avery minor shrinkage and even under high of the sintered dolomite,casting the resulting aqueous ad- I temperatures no disturbing crackswill occur, even more miXtllfe in molds, expanding the admixture by thef so if the brick have been well shaken or rammed down. eration of gasfrom Such agent and hydraullcally Semng 1 Just as in the production ofthe usual cement-bound the stabilized sintered dolomite inahardenedporous form,

Patented May 19, 1964 3 133 822 blocks can be produced of mostlysingle-grain tempered METHODS OF M AKfiqG LIGHT WEIGHT HEAT material orof one with any kind of grain combination.

INSULATING BLOCKS The following examples are given by way of illustrat-Josef Wuhrer, Wulfrath, Rhineland, and Frederick single-grain concrete,or of concrete with any desired grain aggregate in the admixture, sohere also light-weight ing our invention, viz.

comminuting the hydraulically set porous form into granules no largerthan 200 mm., heating such granules to a temperature within the range ofabout 1200 C. to about 1500 C. for about 5 to about 40 hours to shrinkthe granules, removing from the shrunk granules those having a grainsize approximately within the range of about 7 mm. to about 15 mm.,admixing with a bonding amount of fresh non-expanded stabilized sinteredhydraulicallysettable dolomite sufiicient of said removed granules toprovide in the resulting admixture a reduced tendency to shrink andcrack when hydraulically set, then adding a sufiicient amount of waterto effect hydraulical setting of the dolomite, and finally hydraulicallysetting said dolomite with the water to form such heat insulating body.

2. A method of producing a light-weight, heat insulating body having areduced tendency to shrink and form cracks comprising the steps ofadmixing stabilized sintered hydraulically settable dolomite withsufficient water to form a hydraulically-settable pulp and with asufficient amount of a vaporizable metallic gas-producing agent toeffect expansion of such sintered dolomite to a porous form, molding theadmixture, expanding the admixture by the generation of gas from suchagent to such porous form and hydraulically setting the resultingstabilized sintered porous dolomite, granulating the set sintered porousdolomite, heating the resulting granules to a temperature within a rangeof about 1200 C. to about 1500 C. for about 5 to about 40 hours toshrink the granules, admixing a bonding amount of fresh non-expandedstabilized sintered hydraulically-settable dolomite sufficient of saidshrunk granules to provide in the resulting admixture a reduced tendencyto shrink and crack when hydraulically set, and finally adding to theseadmixed granules suflicient water hydraulically to set the admixture andform such heat insulating body.

3. A method of producing a light-weight, heat insulating body having areduced tendency to shrink and form cracks comprising the steps ofadmixing stabilized sintered hydraulically-settable dolomite withsufiicient water to form a hydraulically-settable pulp and with asufiicient amount of a vaporizable gas-producing agent to effectexpansion of said sintered dolomite to a porous form, expanding theadmixture by the generation of gas from such agent to such porous formand hydraulically setting the resulting stabilized sintered porousdolomite, granulating the set sintered porous dolomite, heating theresulting granules to a temperature within a range of about 1200 C. toabout 1500 C. for about 5 to about hours to shrink the granules,admixing with at least a bonding amount of non-expanded stabilizedsintered hydraulically settable dolomite sufilcient of said shrunkgranules to provide in the resulting admixture a reduced tendency toshrink and crack when hydraulically set, and finally adding to theadmixed granules sufiicient water hydraulically to set said granules andform the heat insulating body.

4. The method of claim 3 wherein the porous hydraulically set, sintereddolomite granules are smaller than 200 mm.

5. The method of claim 3 wherein the porous, hydraulically set sintereddolomite is reduced to granules of approximately 7 to 15 mm. beforebeing heated, and such unshrunk granules comprise about 20 percent byweight of the admixture.

References Cited in the file of this patent UNITED STATES PATENTS1,063,102 Baker May 27, 1913 1,994,377 Williams et a1. Mar. 12, 19352,131,374 Grunwald Sept. 27, 1938 2,663,647 Huntzicker Dec. 22, 1953

1. A METHOD OF PRODUCING A LIGHT-WEIGHT, HEAT INSULATING BODY HAVING AREDUCED TENDENCY TO SHRING AND FORM CRACKS COMPRISING THE STEPS OFADMIXING STABILIZED SINTERED HYDRAULICALLY SETTABLE DOLMITE, AT LEAST 96PRCENT BY WEIGHT OF WHICH PASSEA A TYLER STANDARD SCREEN SIZE OF 170,WITH SUFFICIENT WATER TO FORM CASTABLE HYDRAULICALLY SETTABLE PULP ANDWITH A METALLIC PORE-PRODUCING AGENT SELECTED FROM THE GROUP CONSISTINGOF ALUMINUM AND MAGNESUIM PRESENT IN AN AMOUNT SUFFICIENT TO EFFECTEXPANSION OF THE SINTERED DOLOMITE, CASTING THE RESULTING AQUEOUSADMIXTURE IN MOLDS, EXPANDING THE ADMIXTURE BY THE GENERATION OF GASFROM SUCH AGENT AND HYDRAULICALLY SETTING THE STABILIZED SINTEREDDOLOMITE IN A HARDENED POROUS FORM, COMMINUTING THE HYDRAULICALLY SETPOROUS FORM INTO GRANULES NO LARGER THAN 200 MM., HEATING SUCH GRANULESTO A TEMPERATURE WITHIN THE RANGE OF ABOUT 1200*C. TO ABOUT 1500*C. FORABUT 5 TO ABOUT 40 HOURS TO SHRINK THE GRANULES, REMOVING FROM THESHRUNK GRANULES THOSE HAVING A GRAIN SIZE APPROXIMTELY WITHIN THE RANGEOF ABOUT 7 MM. TO ABOUT 15 MM., ADMIXING WITH A BONDING AMOUNT OF FRESHNON-EXPANDED STABILIZED SINTERED HYDRAULICALLYSETTABLE DOLOMITESUFFICIENT OF SAID REMOVED GRANULES TO PROVIDE IN THE RESULTINGADMIXTURE A REDUCED TENDENCY TO SHRINK AND CRACK WHEN HYDRAULICALLY SET,THEN ADDING A SUFFICIENT AMOUNT OF WATER TO EFFECT HYDRAULICAL SETTINGOF THE DOLOMITE, AND FINALLY HYDRAULICALLY SETTING SAID DOLOMITE WITHWATER TO FORM SUCH HEAT INSULATING BODY.